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United States Patent |
5,043,794
|
Tai
,   et al.
|
August 27, 1991
|
Integrated circuit package and compact assemblies thereof
Abstract
In accordance with the present invention, an integrated circuit package
comprises a thermally conductive plate for receiving an integrated circuit
and an open rectangular structure of conductor and insulator for
surrounding the sides of the circuit and presenting one or more linear
arrays of conductive connectors extending laterally through the
rectangular structure. Preferably the rectangular structure also includes
transverse contacts. Advantageously the plate includes extensions beyond
the rectangular structure for acting as cooling fins on opposing sides of
the rectangular structure. The linear arrays and cooling fins are
preferably on different pairs of parallel sides.
Inventors:
|
Tai; King L. (Berkeley Heights, NJ);
Thomson, Jr.; John (Spring Lake, NJ)
|
Assignee:
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AT&T Bell Laboratories (Murray Hill, NJ)
|
Appl. No.:
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587308 |
Filed:
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September 24, 1990 |
Current U.S. Class: |
257/686; 257/705; 257/722; 257/E23.004; 257/E23.103; 257/E25.023 |
Intern'l Class: |
H01L 023/12; H01L 023/14; H01L 023/32 |
Field of Search: |
357/75,74,81,72,80
|
References Cited
U.S. Patent Documents
4631572 | Dec., 1986 | Zimmerman | 357/74.
|
4638348 | Jan., 1987 | Brown et al. | 357/74.
|
4654694 | Mar., 1987 | Val | 357/74.
|
4879588 | Nov., 1989 | Ohsuka et al. | 357/74.
|
4890153 | Dec., 1989 | Wu | 357/74.
|
4894706 | Jan., 1990 | Sato et al. | 357/75.
|
4953005 | Aug., 1990 | Carlson | 357/75.
|
4956694 | Sep., 1990 | Eide | 357/74.
|
Primary Examiner: Hille; Rolf
Assistant Examiner: Clark; S. V.
Attorney, Agent or Firm: Books; Glenn E.
Claims
We claim:
1. An assembly of electrically interconnectable integrated circuit packages
comprising:
(a) a plurality of rectangular integrated circuit packages, each package
comprising:
(1) a thermally conductive plate for supporting an integrated circuit,
(2) an open rectangular structure having a central opening, exterior
transverse surfaces and interior peripheral surfaces with respect to said
opening and parallel lateral surfaces, said rectangular structure mounted
on said conductive plate with said interior peripheral surfaces positioned
for extending around the periphery of an integrated circuit,
(3) at least one interior peripheral surface presenting at least one linear
array of contact means for interconnection with contacts on said
integrated circuit, each of said contact means provided with electrical
connection means extending laterally through said rectangular structure to
a respective exterior transverse surface and each of said contact means
provided with electrical connection means extending transversely through
said rectangular structure to the overlying lateral surface,
(b) alignment means for aligning said plurality of rectangular packages
stacked with their exterior transverse surfaces aligned to form one or
more contact planes; and
(c) interconnect means disposed between successive stacked packages for
interconnecting transverse contacts on the top lateral surface of each
package with the bottom lateral surface of any next successive package
whereby said stacked packages in said assembly are electrically
interconnectable.
2. An assembly of integrated circuit packages according to claim 1 wherein
a plurality of said packages have thermally conductive plates with
portions extending beyond the exterior transverse surfaces of said
packages for acting as cooling fins.
3. An assembly of integrated circuit packages according to claim 1 wherein
said alignment means comprise aligned transverse openings in the corner
regions of respective packages and bolt means through said openings for
securing said packages together in alignment.
4. An assembly of integrated circuit packages according to claim 1 wherein
said contacts laterally extending to exterior transverse surfaces are
plated with conductive material to enhance electrical contact.
5. A linear cluster of integrated circuit assemblies comprising:
a plurality of integrated circuit assemblies according to claim 1, said
assemblies disposed in a linear array with a contact plane of each
respective assembly opposing and contacting a contact plane of at least
one other assembly.
6. A linear cluster of integrated circuit assemblies comprising:
three integrated circuit assemblies according to claim 1, said assemblies
disposed in a linear array with a square contact array of each respective
assembly opposing a square contact array of at least one other assembly,
the middle assembly of said linear array being rotated by 90.degree. about
the axis of said array so that each integrated circuit package of said
middle assembly has at least one contact with every integrated circuit
package of each neighboring assembly.
7. A rectangular cluster of integrated circuit assemblies comprising:
a plurality of integrated circuit assemblies according to claim 1, said
assemblies disposed in a rectangular array with a contact plane of each
respective assembly opposing and contacting a contact plane of at least
one other assembly.
Description
FIELD OF THE INVENTION
This invention relates to packaging for integrated circuits and, in
particular, to an integrated circuit package particularly adapted for use
in compact assemblies and clusters requiring a high degree of
interconnection.
BACKGROUND OF THE INVENTION
As integrated circuits become increasingly complex and are used in
assemblies to perform increasingly complex electronic functions, the
necessity of providing interconnection paths among circuits and circuit
assemblies becomes increasingly a limit on design. For example, in a
number of applications the traditional dual-in-line integrated circuit
package (DIP) simply cannot provide an adequate number of
interconnections, and it has been necessary to go to a new form of
integrated circuit packaging such as a package providing a two dimensional
grid of interconnect pins. Such pin grid arrays (PGA) are not only bulky
but also are delicate and expensive to make.
SUMMARY OF THE INVENTION
In accordance with the present invention, an integrated circuit package
comprises a thermally conductive plate for receiving an integrated circuit
and an open rectangular structure of conductor and insulator for
surrounding the sides of the circuit and presenting one or more linear
arrays of conductive connectors extending laterally through the
rectangular structure. Preferably the rectangular structure also includes
transverse contacts. Advantageously the plate includes extensions beyond
the rectangular structure for acting as cooling fins on opposing sides of
the rectangular structure.
The integrated circuit package of the invention permits the aggregation of
packages into assemblies and into clusters of assemblies rich in
interconnections. Vertically stacked packages form a rectangular
parallelepiped having a plurality of parallel planar cooling fins
projecting from two opposing surfaces and another pair of planar surfaces
providing rectangular arrays of contacts to the enclosed integrated
circuits. In addition, transverse contacts permit electrical
interconnection of the stacked packages.
Linear clusters can be aggregated as a linear array of such assemblies with
their contact surfaces interconnected either directly by an
anisotropically conducting plane or indirectly by an intervening
transformation plane. In a preferred linear cluster, successive assemblies
are rotated by 90.degree. with respect to the axis of the array. In such
clusters each package in the rotated assembly contacts each package in the
neighboring assemblies. In low power equipment, elimination of the cooling
fins permits even higher levels of interconnection such as rectangular
clusters of assemblies.
BRIEF DESCRIPTION OF THE DRAWINGS
The advantages, nature and various additional features of the invention
will appear more fully upon consideration of the illustrative embodiments
now to be described in detail in connection with the accompanying
drawings. In the drawings:
FIG. 1 is a schematic illustration of a preferred embodiment of an
integrated circuit package in accordance with the invention.
FIG. 2 shows the package of FIG. 1 with an integrated circuit in place.
FIG. 3 is a schematic cross section of the structure of FIG. 2 useful in
showing the interconnections which can be provided by the invention.
FIG. 4 is an enlarged, exploded view of components used in making an
integrated circuit package in accordance with the invention.
FIG. 5 is a schematic illustration of a stacked assembly of integrated
circuits packaged in accordance with the invention.
FIG. 6 is a schematic illustration of a linear cluster comprising a linear
array of stacked assemblies of the type shown in FIG. 5.
FIG. 7 illustrates a particularly advantageous embodiment of a linear
cluster.
And FIG. 8 illustrates a rectangular cluster of stacked assemblies.
It is to be understood that these drawings are for purposes of illustrating
the concepts of the invention and are not to scale. Similar structural
elements are denoted by the same reference numeral throughout the drawings
.
DETAILED DESCRIPTION
Referring to the drawings, FIG. 1 shows a preferred embodiment of an
integrated circuit package 10 in accordance with the invention comprising
a thermally conductive plate 11 and an open rectangular structure 20,
comprising layers of conductor and insulator and presenting one or more
linear arrays of electrically conductive bonding pads. Preferably side 20A
provides a lower linear array of bonding pads (B.sub.11, B.sub.12, . . . ,
B.sub.1n) and an upper linear array (B.sub.21, B.sub.22, . . . ,
B.sub.2n). Opposing side 20B provides lower array (B.sub.31, B.sub.32, . .
. , B.sub.3n) (not shown) and upper array (B.sub.41, B.sub.42, . . . ,
B.sub.4n) (not shown). (As better shown in FIG. 3, the arrays of bonding
pads are preferably presented on one or more stepped levels on the
interior periphery of rectangular structure 20). Each of the bonding pads
B.sub.ij is provided with lateral conductive connecting portion extending
laterally from the bonding pad on the inside edge of the rectangular
structure 20, through the structure to a respective lateral contact
L.sub.ij on the transverse outside edge of 20. (The internal connections
are illustrated in the cross section of FIG. 3.) Preferably each bonding
pad B.sub.ij is also conductively connected through the rectangular
structure 20 to a respective transverse contact T.sub.ij on a lateral edge
of 20. The transverse contacts can extend completely through structure 20
to provide contact points T.sub.ij on both the upper lateral surface of 20
and the lower lateral surface (not shown in FIG. 1). Preferably plate 11
includes fin regions 12 extending beyond the external edges of rectangular
structure 20 for acting as cooling fins. Conveniently the linear arrays
B.sub.ij and the cooling fins 12 are on different pairs of opposing
parallel sides of 20.
Advantageously rectangular structure 20 is provided with alignment means
such as a plurality of openings 25, one in each corner, for use in
aligning a plurality of such structures in an assembly.
As better shown in FIG. 2, the central opening in rectangular structure 20
is chosen so that the structure 20 can receive and laterally surround an
integrated circuit 200 mounted on plate 11. The circuit 200 comprises a
set of contacts C.sub.1, C.sub.2, . . . , C.sub.n to which interconnection
is desired, and these contacts C.sub.i are electrically connected to the
set of bonding pads B.sub.ij preferably by gold wire bonds 210 in
accordance with techniques well known in the art.
FIG. 3 is a schematic cross section of the structure of FIG. 2 useful in
showing the interconnections provided by the invention. For example,
contact C.sub.1 on integrated circuit can be connected by wire 210 to
bonding pad B.sub.14 which, in turn, is connected to lateral contact point
L.sub.14 and transverse contact T.sub.14. Similarly, C.sub.2 is connected
to bonding pad B.sub.24 and thence to L.sub.24 and T.sub.24.
The structure and fabrication of the package of FIGS. 1 and 2 can be better
understood by reference to FIG. 4 which is an exploded view showing the
principal components used in making a preferred rectangular structure 20.
In essence the structure 20 is built of a plurality of layers L.sub.1
through L.sub.6 of unsintered ceramic tape having an array of registered
drilled apertures (D.sub.11, D.sub.12, D.sub.13, D.sub.14, D.sub.21. . . ,
D.sub.m4) in which transverse conductive connectors T.sub.ij can be
formed. And upon the layers are printed conductive segments forming the
lateral conductive connectors L.sub.ij. As illustratively shown, the
interior transverse surface of the rectangular structure (the surface
facing into the central opening) presents two linear arrays of bonding
pads B.sub.ij and one pair of bonding pads from each array is mapped into
a single column of conductively filled apertures D.sub.ij. Specifically,
as shown, pads B.sub.15 and B.sub.16 of the lower array and pads B.sub.25
and B.sub.26 of the upper array are connected by conductively filled
apertures to transverse contacts T.sub.16, T.sub.15, T.sub.25 and
T.sub.26. Also as shown, the lateral connections can effect crossovers by
going up a level or down a level as is done in connecting B.sub.16 to L
.sub.16 and B.sub.26 to L.sub.26.
In the preferred embodiment, the ceramic layers L.sub.1 -L.sub.6 are
comprised of 0.04 inch thick green ceramic tape--a mixture of aluminum
oxide ceramic powder and organic binder--such as Coors ceramic tape
available from Coors Ceramic Corporation, Boulder, Colo. The apertures
D.sub.ij can be 141/2 mils in diameter, and both the transverse and
lateral connectors can be metallized with a screen printable ink
containing tungsten metal particles such as Tungsten Ink marketed by
Cernonics, Inc., Matawan, N.J. The conductive plate 11 can be a
tungsten-copper alloy, such as Elkinite, having a coefficient of thermal
expansion compatible with the ceramic. After the unsintered ceramic tape
is imprinted with tungsten ink to form the desired conductive patterns,
the layers L.sub.1 -L.sub.6 are assembled in proper order and
registration, pressed together at a pressure of 500 pounds per square inch
and heated to a temperature of 70.degree. C. for about 1 min to soften the
binder and cause the individual layers to bond together. Final
consolidation of the structure is effected by co-sintering the ceramic and
the tungsten, as by sintering at 1625.degree..+-.25.degree. C. for 2 to 8
hours in a wet (dew point 70.degree. C.) 80% N.sub.2 by volume, 20%
H.sub.2 furnace atmosphere. The exposed metallized areas of the structure
can then be electroplated with a pure nickel film about 0.0005 inch thick.
Conductive plate 11 is then brazed to the lower lateral surface, and the
metallized areas of the structure and the conductive plate can be
electroplated with a gold film about 0.0002 inch thick. The result is an
integral structure 20 with internal transverse and lateral connectors.
Thus an integrated circuit package in accordance with the invention
comprises (1) a thermally conductive plate for supporting an integrated
circuit and (2) an open rectangular structure having a central opening,
exterior and interior transverse surfaces with respect to the central
opening and parallel lateral surfaces. The rectangular structure is
mounted on the conductive plate with the interior transverse surfaces
positioned for extending around the periphery of the integrated circuit.
At least one of the interior transverse surfaces of the rectangular
structure presents at least one linear array of contact means (bonding
pads) for interconnection with contacts on the integrated circuit. Each of
the contact means is provided with an electrical connection laterally
through the rectangular structure to the exterior transverse surface, and
each of the contact means is provided with an electrical connection
transversely through the rectangular structure to the overlying lateral
surface. Preferably each one of a pair of opposing interior transverse
surfaces of the open rectangular structure presents two linear arrays of
contact means (bonding pads) for interconnection with contacts on the
integrated circuit. In addition, the thermally conductive plate has
portions extending beyond the exterior transverse surfaces of the other
(remaining) pair of opposing surfaces for acting as cooling fins.
Preferably the rectangular structure is provided with alignment means for
aligning a bottom lateral surface of the package upon a top lateral
surface of another such package. This alignment means can be a set of
drilled openings in each of the four corner regions extending transversely
through the rectangular structure.
Advantages of the invention will become clearer by reference to FIG. 5
which is a schematic illustration of a stacked assembly 400 of integrated
circuit packages in accordance with the invention. Specifically, a
plurality of m similarly oriented packages 10 are stacked one on top of
the other to form a rectangular parallelpiped having a plurality of
parallel planar cooling fins 12 projecting from a first pair of aligned
transverse surfaces 410A and 410B and a second pair of aligned transverse
surfaces 420A and 420B providing planar rectangular arrays 430 of lateral
contact points to the enclosed integrated circuits. The surface area of
each contact point (L.sub.ij of FIGS. 1-4) can be enhanced by depositing
an array of gold pads onto the contact points. The result is a rectangular
2 MXN array of plated contacts (P.sub.11, . . . , P.sub.2mn), with each
contact of the 2M rows electrically contacting a bonding pad B.sub.ij and
which, in turn, can be connected to a contact C.sub.i of an enclosed
integrated circuit 200 (not shown). This planar array 430 defines a
contact plane which can be used in interconnecting assemblies.
Interconnection between the transverse contacts T.sub.ij of the respective
stacked packages can be facilitated by disposing between the packages thin
sheets of anisotropic conductive material (not shown) such as the 25 mil
EPCI material marketed by AT&T Microelectronics, Allentown, Pa. This
material, comprising conductive particles in a silicone binding,
selectively conducts in regions of compression between overlying contact
points. Alternatively, if transverse interconnection is not desired, a
thin insulating layer such as mylar can be interposed. Preferably the
stacked assembly is bolted together by threaded vertical rods 440, through
respective corresponding apertures 25 in each corner of each package 10.
Thus an assembly of integrated circuit packages in accordance with the
invention comprises a plurality of integrated circuit packages, as
described above, stacked one above the other with their respective
exterior transverse surfaces aligned in a contact plane. Preferably the
respective cooling fin portions are oriented in the same direction, the
transverse openings in the corner regions are in alignment, and the
plurality of packages is secured together in alignment by a rigid bolt
through the aligned openings.
As shown in FIG. 6, larger scale interconnections can comprise a linear
cluster 500 of plural assemblies 400A, 400B and 400C. The stacked
assemblies are preferably oriented with their respective contact surfaces
(not shown) parallel and adjacent. Preferably the arrangement is designed
so that desired interconnections between one assembly, e.g., 400A, and the
adjacent assembly, e.g. 400B, are effected by contact between a contact
plane 430 of 400A (not shown) and a contact plane 430 of 400B. Such
contact can be facilitated by interposing a sheet 550 of EPCI material
between the planar arrays. Thus the contacts of 400A, i.e. the set
P.sub.ij would contact respective contacts P'.sub.ij of 400B. However if
the assembly is not so designed, a transformation plane 560 can be
disposed between 400A and 400B, to provide by suitable insulated
interconnections, any desired mapping of contacts P.sub.ij into contacts
P'.sub.ij.
FIG. 7 shows a particularly advantageous embodiment of the invention
comprising a linear cluster 500 of plural assemblies 400A, 400B, and 400C
similar to the cluster shown in FIG. 6 except that the middle assembly
400B is rotated 90.degree. about the axis of the array.
The contact planar arrays 430 of assembly 400B preferably each provide a
square m.times.m matrix of contact points P.sub.ij where m is the number
of packages in assembly 400B. Similarly, assemblies 400A and 400C each
comprise m packages and preferably each provide a contact planar array
comprising a m.times.m matrix of contact points. Thus when assembly 400B
is rotated by 90.degree. as shown, each package in assembly 400B is
provided contact with each of the m packages in assembly 400C on the right
and with each of the m packages in assembly 400A on the left. Thus each
integrated circuit in assembly 400B can be provided contact with each
integrated circuit in the entire cluster.
Clearly this linear cluster could be lengthened, as by adding an additional
assembly 400D (not shown) rotated by 90.degree. so that 400D is oriented
similar to 400B. 400D would provide each of its packages contact with each
of the m packages in neighboring assembly 400C.
Thus a linear cluster of assemblies of integrated circuit packages in
accordance with the invention comprises a plurality of integrated circuit
assemblies, as described above, disposed in a linear array with a contact
plane of each respective assembly opposing and contacting a contact plane
of at least one other assembly. Preferably the cluster comprises at least
three integrated circuit assemblies each having square contact matrices,
and the middle assembly of the linear array is rotated by 90.degree. about
the axis of the array so that each integrated circuit package of the
middle assembly has at least one contact with every integrated circuit
package of each neighboring assembly.
In applications where cooling fins are not required for heat dissipation
even larger scale clusters can be provided as shwon schematically in FIG.
8. Here each package 400A-400I has been modified by the elimination of
fins on one or both sides and interconnections through the packages are
provided on the sides where the fins have been removed. Stacked assemblies
are then disposed in a rectangular array with each assembly electrically
interconnected to one or more of its neighbors as described above. It is
thus seen that the integrated circuit package of the invention provides a
wide variety of highly compact assemblies and clusters rich in
interconnections among the enclosed circuits.
It is to be understood that the above-described embodiments are
illustrative of only a few of the many possible specific embodiments which
can represent applications of the principles of the invention. Numerous
and varied other arrangements can be readily devised in accordance with
these principles by those skilled in the art without departing from the
spirit and scope of the invention.
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